No U.S. airlines were in the cheapest 50 airlines, which all came in at $0.14 or less. When it came to international travel, the study found that Asian airlines had the lowest cost flights. The cheapest was AirAsiaX, followed by Air India Express, Indonesia AirAsia, Primera Air, and IndiGo Airlines.When to buy the cheapest airline tickets?
Buy the tickets at least two weeks in advance to find better deals. The best time to buy cheap, domestic flight tickets is three weeks before the plane leaves.